High energy slurry explosives

ABSTRACT

A method of testing the uniformity of liner effectiveness. Randomly selected shaped bomblet cases are uniformly filled with a slurry explosive. The cases are fired into armor plate targets and the relative uniformity of penetration between bomblet cases is measured.

United States Patent [1 1 Mallory HIGH ENERGY SLURRY EXPLOSIVES [75]Inventor: H. Dean Mallory, China Lake, Calif.

[73] Assignee: The United States of America as represented by theSecretary of the Navy, Washington, DC.

22 Filed: Aug. 30, 1971 21 App1.No.: 176,265

[52] US. Cl.

[51] Int. Cl. G011 5/14 [58] Field of Search 73/35, 167; 149/91,

[56] References Cited UNITED STATES PATENTS 3,194,066 7/1965 Schwab eta1 73/167 [4 Dec. 25, 1973 2,459,156 1/1949 Ferguson 73/167 3,378,4164/1968 Perry et a1. 149/22 3,356,544 12/1967 Fee et a1. 149/91 3,515,6046/1970 l-lamrick 149/92 Primary Examiner-Herbert Goldstein Att0meyR. S.Sciascia et a1.

[5 7 ABSTRACT 2 Claims, No Drawings 1 HIGH ENERGY SLURRY EXPLOSIVESBACKGROUND OF THE INVENTION The present standard for high energy,castable explosives is Octol which is a binary composition ofCyclotetramethylenetetranitramine (HMX) crystals in a matrix of TNT. Itis made by mixing the high melting point HMX crystals with molten TNT.The hot slurry is then poured or cast into molds or into bomb cases,etc., and allowed to cool so the TNT solidifies. This produces a solidcasting. The principle involved is: before the TNT is solidified, theexplosive consists of uncompressed HMX crystals with all theintercrystalline air displaced by molten TNT. HMX is also known ashomocyclonite or 1, 3, 5, 7 tetranitro -l,3,5,7 tetrazacycle-octane.

Castable explosives which solidify upon cooling or which harden duringstorage have the disadvantage of shrinking, cracking, etc. which is adegrading factor especially noticeable in certain types of warheads.

The use of unpolymerized PBXN-lOl, for example, in some warheads is notsatisfactory since the material will slowly polymerize in storage andbecome hard. Hardening of the explosive is not desirable since warheadfunction may thereby be impaired to the extent that it becomesinoperable. The Octathane or Cyclothane explosives according to thisinvention do not become hard in storage but rather retain their slurrycharacteristics.

Another advantage of Octathane type explosives over unpolymerized PBXN-lOl is that the PBXN-lOl must be premixed before the slurry is pouredinto the warhead. The requirement for premixing requires the slurry tobe pourable which automatically limits the proportion of HMX that can beincorporated in the mixture; this sets a limit on the energy output.

The Octathane explosives have no such limitation since the solidcomponent can be loaded dry or in a partially wet state and theremainder of the liquid nitromethane added at a later stage. Thisloading method can be used because liquid nitromethane or its energyenhanced counterpart has low viscosity and readily wets or soaks intothe solid crystal load and displaces the air. The crystals have ablotter action for nitromethane.

Octol is normally considered as a castable mixture of HMX and TNT. Tomore easily understand this invention, it is helpful to visualize Octolas a gravity packed HMX charge with the interstitial air displaced bymolten TNT which later freezes and produces the solid Octol charge. Theinterstitial air can be displaced by any compatible liquid or liquifiedsubstance. If the liquid is nitromethane, the resultant product isOctathane. If the liquid is molten TNT, the resultant product is Octol.Since nitromethane is less energetic than TNT, Octathane is lesspowerful than Octol. However, the power of Octol could be exceeded bythe use of nitroglycerine or molten TNETB (m.p. 93C) or BTNEN (mp. 945C)as the liquid.

SUMMARY Only two of these mixtures have been given special names: HMXwith nitromethane (Octathane), and cyclotrimethylenetrinitramine (RDX)with nitromethane (Cyclothane). RDX is also known as hexahydro -l,3,5trinitro-S-triazine, cyclonite, hexogen and T4. The low viscosity ofnitromethane gives these particular explosives the property of easilyreproducible loading which is important to the present method and whichcan, only with great effort, be achieved with Octol or Composition B.This reproducibility of loading makes such slurry mixes very useful inthe testing of shaped charge devices of new design before entering intofull scale production.

The sensitivity of Octathane type explosives can be changed by adding afew percent of sensitizing or desensitizing liquid to the nitromethaneliquid phase as is already known to the art. Amines will sensitize andbenzene will desensitize nitromethane. Nitromethane can also besensitized by the addition of nitric acid or tetranitromethane.

Any solid explosive can be used in place of HMX or RDX as the solidphase. However, for high energy output, these materials are preferred.

Any explosive or near-explosive liquid of reasonably low viscosity canbe used in place of nitromethane to displace the intercrystalline air ofthe solid phase. It is of course assumed that the liquid and solid phaseare chemically compatible. Other liquids might at times be desirable tochange the sensitivity or volatility of the final composition.

DESCRIPTION OF THE INVENTION The basic Octathane explosive consists ofHMX crystals with the intercrystalline air displaced by liquidnitromethane. Sufficient liquid nitromethane is used to just displacethe intercrystalline air in order to give the highest possible amount ofHMX both for the high energy potential of the final explosive, and toprevent settling out of HMX crystals in the charge. Used in this way,the nitromethane willdissolve some of the HMX. This can be prevented, ifso desired and in many cases it will be so desired, by saturating thenitromethane with HMX before it is added to the HMX to make theOctathane.

In the basic formulation, Octathane will be slightly less energetic thanOctol because the nitromethane used to displace intercrystalline air isless energetic than TNT. However, an energy enhanced Octathane can bemade by dissolving RDX in nitromethane (nitromethane will dissolve asmall amount of RDX) and using this solution to formulate the Octathane.Other explosive or energetic nitrated materials of greater solubilitythan RDX may'be dissolved in the nitromethane to increase its energy.However, the solution of large quantities of other materials in thenitromethane may overly increase its viscosity making it more difficultfor the liquid to displace the intercrystalline air of the HMX.

Instead of Octathane (HMX and nitromethane) a similar but lower energyexplosive, Cyclothane, can be made by combining RDX crystals withnitromethane (with or without the prior solution of RDX in the liquidnitromethane). If the nitromethane is used without previously saturatingit with RDX, some of the RDX will dissolve in the liquid nitromethaneafter the components are mixed. An indication of the degree of solutioncan be gained by noting that the density of nitromethane is 1.129 (2 3/4g/ml and the density of HMX saturated nitromethane is 1.132 (2 3/4) g/mland the density of RDX saturated nitromethane is 1.145 (2 3/4) g/ml.

UTILITY The use of an explosive mixture according to the presentinvention can best be illustrated by a description of the operationsperformed in loading and testing cone shaped cluster bomblets withcopper liners for reproducibility of said liners. Through an open portabove the cone apex, nitromethane was poured in until the bomblet casewas half full. Dry, class A, HMX was then sifted in with tapping todislodge air bubbles. Since nitromethane is a thin, mobile liquid ofmuch lower density (1.13 g/cc) than HMX (1.90 glcc), the HMX crystalsquickly sink to the bottom of the container, shedding air bubbles asthey drop. This results in very well packed HMX around the cone whereloading reproducibility is so important for test purposes. There is notendency toward segregation as in Octol since nitromethane cannot holdHMX in suspension as can the more viscous, higher density, molten TNT.HMX was added until it reached the top of the charge; any excess liquidwas blotted up with a paper towel.

The bomblets were then fired at probe standoff into armor plate targets.Firing was done without the usual impact sensing element and fuse wirerunning from the probe to the base fuse. Test results, therefore, showedthe reproducibility of two things l) the explosive load,

and (2) the copper liner. A group of 6 bomblets so detonated gave thefollowing mean penetration and stan- 4 dard deviation:

i 7.12 inches i 0.46 inches.

These results were confirmed by loading and firing a second group of 19production run bomblets. These gave 7.21 inches :t 0.48 inches.

Given the controlled uniformity of the explosive charge, the relativelysmall deviations in penetration indicates the uniformity in performanceof the production reen copper liners. What is claimed is: 1. A method oftesting uniformity of liner effectiveness in shaped charge explosivedevices comprising:

uniformly filling randomly selected shaped charge bomblet cases havingcopper liners with a slurry explosive selected from the group consistingof HMX with nitromethane and RDX with nitromethane;

firing the cases so filled at a predetermined stand-off into armor platetargets; and

measuring the degree of penetration of the target material and relativeuniformity of penetration between bomblet liners.

2. The method of claim 1 wherein the explosive mix consists of HMX andnitromethane and wherein the bomblet casing is half filled withnitromethane and thereafter dry crystalline HMX is sifted in whiletapping to dislodge air bubbles.

1. A method of testing uniformity of liner effectiveness in shapedcharge explosive devices comprising: uniformly filling randomly selectedshaped charge bomblet cases having copper liners with a slurry explosiveselected from the group consisting of HMX with nitromethane and RDX withnitromethane; firing the cases so filled at a predetermined stand-offinto armor plate targets; and measuring the degree of penetration of thetarget material and relative uniformity of penetration between bombletliners.
 2. The method of claim 1 wherein the explosive mix consists ofHMX and nitromethane and wherein the bomblet casing is half filled withnitromethane and thereafter dry crystalline HMX is sifted in whiletapping to dislodge air bubbles.